Not Applicable
Not Applicable
This invention relates to piston pumps and compressors, and more particularly to a connecting rod with an integral grease reservoir for use in piston pumps and compressors.
Small-scale air compressors are often used to power nebulizers. A typical type of compressor for that purpose uses a wobble piston. Examples of such compressors are found in U.S. Pat. No. 3,961,868, issued Jun. 8, 1976 to Arthur J. Droege, Sr. et al, for xe2x80x9cAir Compressorxe2x80x9d and U.S. Pat. No. 4,842,498, issued Jun. 27, 1989 to Roy J. Rozek, for xe2x80x9cDiaphragm Compressorxe2x80x9d.
In a typical compressor, a piston reciprocates in a cylinder sleeve to compress air. The piston is a plastic connecting rod having a piston end disposed in the cylinder sleeve, and a connecting end connected to an eccentric component mounted to a shaft. As the shaft rotates, the connecting rod having a piston head disposed in a cylinder sleeve reciprocates to compress air. In one prior art compressor, the connecting rod end includes a ball bearing as the interface between the rod and the eccentric component. In another form of prior art, the rod does not include a ball bearing. Instead, a pin projecting from the eccentric component is slidably inserted into a bore formed in the connecting end. This design relies on the free rotation of the pin within the bore.
The bore is preferably formed to have an interior diameter which is substantially equal to the outside diameter of the pin to avoid chatter. Some form of lubrication is provided in this assembly to enhance the life of the bore. The lubrication method typically used includes an oil saturated felt wick that makes contact with the side of the pin, this contact occurring though a small hole in the side of the rod end. Lubrication of the bore occurs by means of capillary action drawing oil from the wick, into the bore. This design concept has proved unreliable due to problems with drying of the wick, wick becoming dislodged during operation, or poor capillary lubrication. Therefore, a need existed for a means to easily assembly and reliably lubricate the pin within the bore.
The present invention provides a connecting rod including a generally vertical oriented rod section having a piston end and a connecting end. A bore is formed in the connecting end for receiving a pin mounted eccentrically on a shaft. The bore is open on only one end, creating a closed reservoir at the inside end of the bore. Since the bore diameter is substantially equal to the pin diameter, assembling the pin to the rod could be difficult due to hydrostatic pressures created from the tight fitting parts. As a means to facilitate this assembly, a groove is provided through the length of the bore, acting as an escape path for any entrapped air.
This groove also provides escape for excess lubrication media. This groove has an additional benefit in that the lubrication media is now available over the length of the pin, providing lubrication to the entire surface during the initial rotations of the pin. The lubrication media within the reservoir end is protected from environmental contamination and drying, and is available throughout the life of the unit to provide lubrication to the pin.
The general objective of providing a connecting rod having a bore in which a pin is easily inserted is accomplished by providing the bore with an axial groove. The groove provides an escape path for air and lubricant trapped in the bore during assembly.
Another objective of the present invention is to provide a connecting rod having a bore in which a pin is lubricated over the entire length of the pin. This objective is accomplished by providing an axial groove along the entire length of the bore to provide lubricant along the entire length of the pin.
Another objective to the present invention is to provide a method to lubricate the pin that is reliable and to maintain the lubrication media within the connecting rod during the entire operating life of the compressor.
The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention.